P0404
Exhaust Gas Recirculation Control Circuit Range/Performance
- Severity
- Medium
- Driving
- Drivable — book it in
The EGR control circuit is electrically intact but the valve is not doing what it is told - it moves too slowly, does not reach the commanded position, or sticks part way. This is the code that typically appears when a valve is on its way out rather than already dead, and on an electronically actuated valve it commonly means carbon is making the valve stiff.
Possible causes
- CommonCarbon making the valve stiff or preventing full travel
- CommonWorn or failing EGR valve motor
- PossibleFaulty EGR position sensor giving an inaccurate position
- PossibleHigh resistance in the wiring, weakening the drive to the motor
- PossibleMechanical obstruction in the valve or passage
What you might notice
- Check engine light on
- Rough idle or hesitation in some conditions
- Failed emissions test
- Often no symptom the driver notices
What to check, in order
- Compare commanded EGR position against actual position on the live data screen, through a full sweep. A valve that lags, overshoots or stops short is the fault.
- Remove and inspect the valve for carbon. A stiff valve is usually a dirty valve rather than a failed motor.
- Check the harness for high resistance - a corroded pin can pass enough current to drive the valve weakly but not enough to meet the module's timing expectations.
- If the valve is clean, moves freely by hand and the wiring measures good, the actuator or its position sensor is at fault.
- After cleaning or replacing the valve, check whether the manufacturer specifies a relearn or adaptation reset. Some modules keep adapting to the old worn valve until the adaptation is cleared.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499